The hypothesis presented by Todaro (1969) and Harris and Todaro (1970) related to rural-to-urban migration is an important model for migration analysis when people move from rural towns to urban sites. They hypothesize that individuals migrate to urban sectors with the objective of obtaining employment in the formal sector and that informal sector employment is a transitional phase during which migrants are looking for a more formal job. Their seminal work based on a model of interregional migration is characterized by a certain degree of selectivity (Harris and Todaro 1970). The Todaro model suggests that younger migrants increase the time period for expected income. Also, migrants with a higher level of education have a higher probability of obtaining formal employment. Married migrants are expected to have lower level of migration rates, because of the higher costs related to relocation of the whole family (Mincer 1978).
Migration is essentially selective. Despite some exceptions, for example forced migration or movements to colonization projects, the vast majority of migration contain an element of migrant selectivity (also known as differentiation). In general, selectivity occurs because there are distinct differences between the interests of the individuals who belong to various social groups. The most commonly examined personal differences are related to age, gender, level of education, socio-professional status, marital status, and housing situation (owner or renter of property). Consequently, such attitudinal differences are manifested in behavioral differences with respect to staying in or leaving the community (White and Woods 1980). Younger people, for example, are more likely to migrate than older persons.
Figure 3 illustrates an important aspect of migrant selectivity, known as "chain migration" (Cox 1972). This refers to the subsequent migration of families and relatives, following the initial move by the first migrants from a community. As the graphic illustrates, as family or friends migrate, a network of information flows back to the point of origin, reducing the obstacles to migration for later migrants.
Figure 3. Chain Migration and Network Development
Source: Adapted from Muñiz (2006).
The movement of people is also a result of the degree of connectivity within a given system. Connections and subsequent interactions among centers imply specific complementarities. In other words, migration is more likely between two places that have existing connections between them than between places that are disconnected.
Potential migrants are likely to value different attributes of places, to have different information available to them, and therefore to react in different manners. Today, information is widely available and updated through complex networks of professionals and organizations. New worldwide migrants rely on these complex networks, which are dynamic in essence, converting these networks into very sophisticated networking systems. Highly specialized professionals and workers are fed with information and move within these networks to satisfy transnational corporation demands in order to fulfill their activities in different regions of the world.